Means and method of putting mercury in evacuated tubes



g- 1950 J. FREEMAN 2,520,278

MEANS AND METHOD OF PUTTING MERCURY IN EVACUATED TUBES Filed May 15, 1946 Patented Aug. 29, 1950 MEANS AND METHOD OF PUTTING MER- CURY IN EVACUATED TUBES Jacob Freeman, Dorchester, Mass. Application May 1 5, 1946, Serial No. 670,001

2 Claims.

The present invention relates to-a means and method of putting mercury in evacuated or partially evacuated tubes through which electric current is passed for illumination, electrical control, signalling or other purposes.

The present invention applies particularly to tubes used for illuminating purposes such as lighting and signs and also to mercury tubes used for various purposes where ionization and electrical discharge takes place between two electrodes positioned at the ends or somewhere in the tubes.

Tubes of this type usually have a low gas pressure within the tube, the gas being ionized and thereby providing an electrical path for the discharge of the electric current through the tube. In the manufacture of such tubes initially the air in the tube is exhausted by a Vacuum pump after which the tube is filled with gas in the desired amount.

The present invention relates to such tubes in which a small amount of mercury is forced into the tube for the purpose of producing the desired ionization, color effect or other electrical phenomona for which mercury is usually used. The quantity of mercury which is put into the tube is usually very small and since it must be put in after the tube or vessel has been evacuated of air or gases, various methods have been used in the prior art for accomplishing this result. Such methods, however, have not generally provided permanent installations adapted for repeated operation since the tube must be disconnected from the system in which case the vacuum is released. Where some special production methods have been employed, the amount of mercury used does not appear to be accurately controlled or readily handled. In a common method used in the prior art, the mercury is contained in a glass bulb attached to the tube which is being exhausted. When the tube has been exhausted, the unit with the bulb is tipped to permit a little of the mercury to run into the tube from the bulb and then the tube is sealed off and the mercury bulb unit removed, This necessitates removal separately of the bulb containing the mercury and is inefficient in commercial operations.

In accordance with the present invention, the operation of forcing the necessary amount of mercury into the evacuated vessel may be repeated in an efficient production method without removing or disconnecting the mercury supply source at any time even for replenishing the mercury. It is necessary only to connect in the usual manner the high voltage tube for exhaust and when the tube has been exhausted, the mercury may readily be forced into it. The tube is sealed off and the system is ready to receive another tube to be exhausted of air and filled accurately with the proper amount of mercury.

In the system and method of the present invention the apparatus employs no mechanical operable elements. There can be no loss of mercury nor does the apparatus have to be taken apart to refill. The quantity is accurately controlled in small uniform droplets, admitted to the tube under substantially the same conditions at all times. The mercury is completely apart from the pumping system and cannot be drawn into it.

The present invention will be more fully described in connection with the drawing illustrating an embodiment of the same in which:

Figure 1 shows the system in general.

Figure 2 shows an enlargement of the detail of Figure 1, and

Figure 3 shows the article produced in its finished form.

Figure l, I is a tube of glass or other material which is to be exhausted of air either partially or entirely, depending upon its ultimate use. The article as a finished product in Figure 3 is illustrated as an illuminating tube for lighting and sign purposes and may be of the mercury, neon or other type in which a small amount of mercury may be used.

In Figure l the tube i may have en-d sealing elements 2 and 3 sealing in the electrode terminals 6 and l in the usual manner. Between the ends of the tube l is the exhaust connection 8 which has a constriction 5 which is ultimately formed into a seal H as indicated in Figure 3. The exhaust connection 8 is joined at 15 to a permanent pumping system which has the exhaust line 9 joined at d which is directly connected to the vacuum pump it through a valve l4 and line 8. The exhaust line may be supplied with a mercury gauge I5 and there may be other connections to the extension I! for the addition of other elements or gases.

In the structure of Figure 1 it will be noted that the line 9 is connected to the line is by an inverted V branch section I9 having a downwardly vertically extending branch l2 Whose function will now be explained.

It is essential in the present system that the line [9 and 9 have a downward gradient to the tube l and that the branch [2 also extends downward.

As indicated more clearly in Figure 2, the branch 12 has a capillary constriction 20 in its top section at the entrance to the tube IS. The tube I2 is open at its lower end 2| and dips into a top opened tube 22 in which mercury is contained above the lower level of the open end 2|. Within the tube l2 the mercury will stand at the point 23 representing the difierence in pressure between the atmosphere and the exhaust in the line 9 which is the same as that in the tube i.

In the operation of the system the tube I, which is provided with the extension 8, is joined to the system at 4. The pump then draws out the air to the desired pressure as indicated by the mercury gauge. The tube 22 is then raised, raising the level 23 of mercury until a droplet 24 flows through the constriction 20 into the tube [9. More than one droplet may be flowed into the tube l9 and they may be counted so that the amount of mercury admitted is definitely known, the capillary opening regulating accurately the 8126-.

The tube 22 may be filled from the top with mercury when the level is lower than desired.

After the desired number of droplets of mercury has flowed into the tube I the tube may be sealed off as indicated at H (Figure 3) and the rest of the portion of the original structure 8 cut away so that a new tube may be put in place to repeat the operation again.

The system in the present invention is adaptable both for use intubes: used for illumination (in which sometimes various rare gasses may be added) and also in tubes used for electrical communications, power conversion and transformation as well as signalling purposes and other industrial applications.

In the system employed it will be noted that no rubber hose connection or its equivalent is necessary. This eliminates the danger of leakage of air into the system through porousness of the rubber or other equivalent materials and also the likelihood of collapse of rubber hose or difiiculty in maintaining a tight clamping joint.

Having now described my invention, I claim:

1. A system for supplying mercury to an evacuated vessel comprising positioning the evacuated vessel at a desired level, an exhaust line inclined upward from the evacuated vessel, a tube having a capillary constriction at its juncture with the exhaust line, said tube extending downward to the lower level from its point of juncture, an open-ended tube surrounding said first tube and containing mercury therein, said first tube and said open-ended tube forming a mercury seal against the exhaust, said openended tube being of sufficient size so that when it is raised, the level of mercury will enter said constriction and permit droplets of mercury to flow downward into the evacuated vessel.

2. In a system for supplying mercury to an evacuated vessel, an exhaust line connected to the vessel, a tube attached to the exhaust line havin a capillary constriction at its junction therewith, means maintaining a mercury level in said tube between the external atmosphere and the pressure of the exhaust line including a vessel containing mercury surrounding said tube with the mercury extending upwards in the tube forming an air seal, said vessel adapted to be raised to force the mercury level in the tube to be raised through said capillary constriction whereby droplets of mercury may flow downward into the evacuated vessel.

JACOB FREEMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,685,666 Brophy et al Sept. 25, 1928 2,433,177 Wainio l Dec. 23, 1947 

